Method and apparatus for dislodging accumulated dust from dust collecting elements

ABSTRACT

An electrostatic precipitator for industrial dusts has dustcollecting elements mounted for transverse vibration and vibrating means that insures maximum effectiveness in dislodging dust accumulations, without the destructive longitudinal rapping techniques customarily employed by the art. The dust-collecting elements are hinge mounted, either individually on respective axes or collectively on an axis in common, with the hinge axis or axes extending in general parallelism with the transverse vibratory motion, i.e. with the respective waves that travel along the lengths of the elements, so no force moments are transmitted to the supporting structure. Vibratory motion is applied by any suitable means, such as vibrators of various conventional types, through a moment arm located at or adjacent to the hinge mounting. The vibration is preferably controlled so as to match the natural frequency of the dust-collecting elements, and such elements are preferably selected on the basis of possessing easily induced natural frequencies. The entire dust-collecting structure is advantageously resiliently mounted with respect to the enclosing housing and its supporting framework.

United States Patent 91 [111 3,759,014

Van Dyken, H et al. 1 1 Sept. 18, 1973 METHOD AND APPARATUS FOR Primary Examiner-Hemard Nozick DISLODGING ACCUMULATED DUST FROM Attorney-Mallinckrodt & Cornaby, Philip A. Mal- DUST COLLECTING ELEMENTS linckrodt and John L. Sniado [75] Inventors: Harold B. Van Dyken, lI, Keany;

Denard A. Brandt, Tucson Highway,

both of Ariz. [57] ABSTRACT [73] Assignee: Kennecott Copper Corporation, New An electrostatic precipitator for industrial dusts has York, N.Y. dust-collecting elements mounted for transverse vibration and vibratin means that insures maximum effec- [22] Flled: May 1971 tiveness in dislod ging dust accumulations, without the [21] Appl. No.: 142,476 destructive longitudinal rapping techniques customarily employed by the art. The dust-collecting elements are hinge mounted, either individually on respective [52] U.S. Cl 55/96, 5554/1315; 555540404 axes or collectively on an axis in common with the [51] Int Cl 6 3/76 hinge axis or axes extending in general parallelism with l 58] Fie'ld the transverse vibratory motion, i.e. with the respective waves that travel along the lengths of the elements, so no force moments are transmitted to the supporting structure. Vibratory motion is applied by any suitable [56] References cued, means, such as vibrators of various conventional types, UNITED STATES PATENTS through a moment arm located at or adjacent to the 2,893,511 7/1959 Egan 55/112 hinge mounting The vibration is preferably controlled 3,201,923 8/1965 Gustafsson et al 3,212,643 10/1965 Schmidt, Jr. et 211.... 3,587,213 6/1971 Tammy 55/112 so as to match the natural frequency of the dust- 55/300 collecting elements, and such elements are preferably 55/304 selected on the basis of possessing easily induced natu- 3,605,915 9 1971 Gately et al. 55/112 ml frequencies The entire dusbconectmg structure is FOREIGN PATENTS OR APPLICATIONS advantageously resiliently mounted with respect to the 458,872 8/1949 Canada 55 112 enclosing housing and its supporting framework. 656,468 1/1963 Canada 55 112 957,273 5/1964 Great Britain 55 112 13 Clllms, 6 Drawing Figures 00000000000000000000000 a ooooaoocooooooouoo oooooooo oOOoOoOoooocooOoo ooOOooOooOOoOOOOoOO Pmmiusw 3.759.014

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INVENTORS. HAROLD B VAN DYKEN II DENARD A BRANDT M GWIAL'IZI'ORNEYS Pmminw'w 3.759.014

sum a nr 2 FIG. 3

INVENTORS. HAROLD B. VAN DYKEN II DENARD A. BRANDT QI/WJQGZ yak ATT NEYS METHOD AND APPARATUS FOR DISLODGING ACCUMULATED DUST FROM DUST COLLECTING ELEMENTS BACKGROUND OF THE INVENTION 1. Field a i The invention is in the field of dust collecting apparatus, particularly electrostatic precipitators wherein dust particles from passing streams of gaseous fluids are first electrically charged and then deposited on oppositely charged, dust collecting elements.

2. State of the Art Electrostatic precipitators for removing dust particles from industrial gaseous effluents have been known and used extensively for many years. Deposits of accumula ted dust on the dust-collecting elements thereof have customarily been dislodged by repeatedly striking ends of such elements to, in effect, longitudinally shake such elements free of the dust. This has not proven very effective unless carried out so vigorously as to cause serious problems of wear and distortion, some industrial dusts being much more difficult to dislodge than others.

Accordingly, there has long been a need for more effective dust dislodging means and procedures as applied to the dust-collecting elements of electrostatic precipitators and the like. The inducing of transverse vibrations along the length of a dust-collecting element, as contrasted -with customary longitudinal rapping techniques, has been suggested (U.S. Pat. No. 3,086,341) but in a specific manner quite different from that here disclosed.

SUMMARY OF THE INVENTION Very' effective dislodgment of dust, usually as coherant sheets," from the collecting surfaces of dustcollecting elements of electrostatic precipitators is achieved in accordance with the present invention when such elements are suspended individually or in common from a hinge mounting, whose axis extends along and in general parallelism with the width of the element or elements concerned, and when transverse vibration of such element or elements is effected by vibratory means operative on a moment arm projecting transversely from the hinge axis at or adjacent to the hinge mounting.

Hinge mounted as they are, the dust collecting elenie n ts lose a minimum of energy to the supporting structure, and, with the vibratory motion applied to their hinged upper ends, the inertia of their suspended masses, cause transverse vibratory waves to travel downwardly along their lengths.

Those waves are established with minimum input energy if the applied vibrations match the natural frequencies of vibrationof the elements and if such elements have easily induced natural frequencies of vibration.

Isolation of the induced vibrations is achieved if the dust-collecting elements are resiliently mounted with respect to the enclosing housing of the precipitator apparatus and to the structural supporting framework thereof.

THE DRAWINGS Apparatus representing the best mode presently contemplated of carrying out the invention is illustrated by way of example in the accompanying drawings, in which:

FIG. 1 is a fragmentary top plan view of a typical electrostatic precipitator for industrial dusts, embodying the invention;

FIG. 2, a transverse vertical section taken along the line 2-2 of FIG. 1 and drawn to a larger scale, the lower part of the apparatus being broken away venience of illustration;

FIG. 3, a fragmentary longitudinal vertical section taken along the lines 3-3 of FIG. 1 and drawn to a somewhat larger scale than FIG. 2;

FIG. 4, a view similar to that of FIG. 3, but taken along the line 4-4 of FIG. 2 to show a hinge suspension from the resiliently mounted supporting structure in transverse vertical section;

FIG. 5, a similar view taken along the line 5-5 of FIG. 2 to show a preferred vibrator and mounting therefor; and

FIG. 6, a fragmentary pictorial view of dust collecting elements mounted for transverse vibration in common in accordance with the invention as successive series rigidly interconnected at their upper ends and having a common hinge mounting.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Electrostatic precipitators for industrial dusts are constructed in a variety of ways. That shown in FIGS. 1-5 is representative of the general construction and is typical of the manner in which the invention may be adapted to existing types. It comprises an enclosing and heat insulating housing 10 supported by a structural steel framework 11. Dust-laden air or an industrial gas to be relieved of particulate matter carried thereby is admitted to such housing 10 by way of a conduit 12 and the gaseous portion thereof is discharged at the opposite end (not shown) of the housing after passing between electrically grounded dust-collecting panel baffles, indicated generally at 13, FIG. 2. The particulate matter constituting the dust is electrically charged in conventional manner so as to be attracted to and held by the bafi'les as the gaseous stream passes through housing 10.

Although the illustrated bafiles 13 extend transversely across the path of gas flow, others may and usually do extend longitudinally of the direction of gas flow, depending upon particular design characteristics of the precipitator concerned. Moreover, depending upon the width of the percipitator, more than one baffle 13 arranged side-by-side may be required to traverse such width.

In accordance with the invention, the dust-collecting baffles are resiliently mounted with respect to the housing 10 by means of a horizontal structural steel frame 14, which is suspended from the top wall 10a of the housing by means of hanger rods 15 resting on coil springs 16. The weight of the bames is thus directly and resiliently supported by the springs 16. As illustrated in FIG. 3, several of the baffles 13 are conveniently supported in common by the frame 14 and by sets of four of the hanger rods 15 and of the springs 16.

Each of the baffles 13 is made up of a series of elongate dust-collecting elements 17, here shown as structural steel channels although they may be of any suitable configuration and material. In the particular arrangement shown, these elements are spaced apart along and rigidly secured together at their upper ends by tie plates 13a and by an elongate suspension hinge for conmeans therefor. Other arrangements of supporting means and hinge means providing hinged suspensioncan, of course, be employed.

Here, the suspension hinge comprises an elongate eye member 18 rigidly secured to the upper ends of the series of side-by-side dust-collecting elements 17, as by welding, and an elongate hinge pin or pintle 19 whose opposite ends extend into and are supported by respective eyes 20 secured, as by welding, to frame 14, see FIGS. 2 and 4, and further secured by strap hangers 21. Accordingly, elements 17 are free to vibrate transversely, i.e. back and forth with respect to the suspension hinge axis, so no force moments are imparted to the structural frame 14. Substantially all energy applied for vibration purposes is, therefore, put to useful purpose and vibration is effected to best advantage.

in accordance with the invention, vibratory motion is applied via a moment arm extending transversely with respect-to (and preferably located at or closely adjacent to) the hinge suspension, so as to induce transverse vibratory motion in the respective dust-collecting elements, i.e. waves that travel along the lengths of the elements from the upper ends thereof downwardly. As here shown, moment arms for the respective baffles 13 are provided by brackets 22 fabricated from steel plate to have the necessary strength for the purpose, e.g. with a platform member 22a, FIG. 5, a gusset plate 22b, and a peripheral skirt 220. Accordingly, it is seen that these moment arms are rigidly connected to the dustcollecting elements at or closely adjacent to the upper ends thereof and extend from and transversely of the hinge axes of the respective hinge suspensions.

Any suitable means may be employed to impart vibration to the dust-collecting elements 17 of the baffles 13 through moment arms 22. However, we have found it advantageous to employ a pneumatically actuated device 23, such as that known as the Perm-Lube BH" vibrator manufactured by National Air Vibrator Company, Houston, Texas, and to modify it for the purpose by rigidly attaching a cylindrical spacer 24 to the cylinder 23a thereof, as by means of bolts (not shown)-inserted internally through the bore of cylinder 23a after weighted piston 23b has been removed for the purpose. Spacer 24 is rigidly secured to platform member 22a of the moment arm, as by means of machine screws 25, and the device is protectively housed by a casing 26 that extends through top wall 10a of housing 10 in sealed relationship therewith and that is flexibly sealed to spacer 24 by a tubular diaphragm 27. Pressure air is supplied through a flexible hose 28, passes into the cylinder 23a to excite the vibrator, and is exhausted through cooling passages in the cylinder and finally to atmosphere through a port 26a in the top of casing 26. Arranged andconnected in this manner, piston 23b in effect constitutes a reaction member during periods of resonance about which the cylinder 23a of thedevice vibrates with a very short stroke, in turn vibrating moment arm 22. In this triple baffle arrangement, the moment arm 22 for the intermediate baffle 13, 'see FIG. 3,- projects freely through an accommodating opening in one of the adjoining baffles. i i

The embodiment shown in FIG. 6 is indicative of how a plurality of baffles can be collectively suspended by a single hinge and vibrated by a single vibrator.

Baffles 30 are provided by rigidly attaching, as by welding, a closed box structure 31 to the upper ends of dust-collecting elements 32. A suspension hinge is provided by an elongate eye member 33 rigidly attached to, as'by welding, and extending along the top of box' structure 31. A hinge pin or pintle member 34 extends through such eye member and either through a supportingeye member (not shown) rigidly secured to suitable supporting structure, such as the underside of a beam of structural framework (not shown) of enclosing housing 35, or directly of such structural framework.

A single vibrator 36 is attached to box structure 31 at an outboard location with respect to the axis of the suspension hinge and preferably intermediate the length of such box structure. Thus, such box structure serves, in itself, as a moment arm with respect to the axis of the hinge.

Transverse vibrations are characterized by repeated deflections from one side of the longitudinal axis of a dust-collecting element to the other between a series of nodal locations along the length of the element depending in number upon the mode, i.e. the frequency, of vibration. Transverse stresses are induced thattend to dislodge accumulated dust in sheets. By applying vibratory motion to the dust collecting element or elements through a moment arm with respect to a hinge axis, predominantly transverse vibrations, isolated from the supporting means, are obtained.

Natural frequencies of vibration of any dustcollecting element can be easily calculated by known mathematical procedures and frequencies of the applied vibration can then be matched to these natural frequencies, resulting in maximum excitation of the element.

lt can thus be seen that the frequency as well as the amplitude of the applied vibration will vary with the physical characteristics of the element or elements concerned and becomes a matter of sound engineering design under the prevailing circumstances.

Typical frequencies of vibration are within the range of from 1,200 to 7,000 cycles per minute and amplitudes within the range of from 0.050 to 0.300 of an inch, but these are not critical because both frequency and amplitude depend upon the physical characteristics of the dust-collecting element as previously indicated.

Whereas this invention is here illustrated and described with respect to certainpreferred forms thereof, it is to be understood that many variations are possible withoutdeparting from the inventive concepts particularly pointed out in the claims.

What is claimed is: v

' 1. Dust collecting apparatus, comprising at least one elongate dust collecting element suspended from an end thereof so as to hang freely for transverse vibration along its length; supporting means for said element; hinge suspension means mounting the upper end of said element on the supporting means for pivotalmovement about a hinge axis; a moment arm rigidly connected with said element substantially at the upper end thereof and extending transverely of said hinge axis; and means for applying vibratory movement to said moment arm longitudinally of said element.

2. Dust collecting apparatus as recited in claim 1, wherein the means for applying vibratory movement is a pneumatic vibrator having a piston and a cylinder, the latter being rigidly secured to the moment arm.

3. Dust collecting apparatus as recited in claim 1, wherein the means for applying vibratory movement to the moment arm is constructed and arranged to apply vibratory movement that substantially matches a natural frequency of vibration of the dust-collecting element.

4. Dust collecting apparatus as recited in claim 1, wherein the dust collecting element is a structural steel shape whose width extends substantially parallel with the hinge axis.

5. Dust collecting apparatus as recited in claim 1, wherein a plurality of the dust collecting elements are rigidly interconnected in common.

6. Dust collecting apparatus as recited in claim 5, wherein the plurality of dust collecting elements are arranged side-by-side in series to form a dust collecting panel.

7. Dust collecting apparatus as recited in claim 5, wherein the plurality of dust collecting elements are spaced relative to each other and are rigidly interconnected by a substantially rectangular structure; the hinge suspension means has one member extending along and secured to said structure intermediate its expanse, so that said structure provides a moment arm with respect to the hinge axis, and has another member pivotally related to said one member and supported by the supporting means.

8. Dust collecting apparatus as recited in claim 5, including means resiliently connecting the rigidly interconnected elements with the supporting means.

9. Dust collecting apparatus as recited in claim 5, wherein there is a plurality of side-by-side series of the dust collecting elements arranged one after the other in file; and means resiliently connecting the said plurality of series with the supporting means in common.

10. Dust collecting apparatus as recited in claim 6, wherein the series of dust collecting elements are spaced from each other and are rigidly interconnected by one member of the hinge suspension means, another member of said means being pivotally related to said one member and supported by the supporting means.

11. Dust collecting apparatus as recited in claim 10, wherein the moment arm extends rigidly from adjacent the one member of the hinge suspension.

12. A method of dislodging accumulated dust from an elongate dust-collecting element, comprising applying vibratory motion to a moment arm attached to the upper end portion of the dust-collecting element, longitudinally of said element and at a location offset laterally therefrom, while freely suspending said element from a hinge axis, said moment arm extending transversely of said hinge axis so as to induce transverse waves that travel downwardly along the length of said element and dislodge said accumulated dust.

13. A method in accordance with claim 12, wherein the vibratory movement substantially matches a natural frequency of vibration of the dust-collecting element. i i i 

2. Dust collecting apparatus as recited in claim 1, wherein the means for applying vibratory movement is a pneumatic vibrator having a piston and a cylinder, the latter being rigidly secured to the moment arm.
 3. Dust collecting apparatus as recited in claim 1, wherein the means for applying vibratory movement to the moment arm is constructed and arranged to apply vibratory movement that substantially matches a natural frequency of vibration of the dust-collecting element.
 4. Dust collecting apparatus as recited in claim 1, wherein the dust collecting element is a structural steel shape whose width extends substantially parallel with the hinge axis.
 5. Dust collecting apparatus as recited in claim 1, wherein a plurality of the dust collecting elements are rigidly interconnected in common.
 6. Dust collecting apparatus as recited in claim 5, wherein the plurality of dust collecting elements are arranged side-by-side in series to form a dust collecting panel.
 7. Dust collecting apparatus as recited in claim 5, wherein the plurality of dust collecting elements are spaced relative to each other and are rigidly interconnected by a substantially rectangular structure; the hinge suspension means has one member extending along and secured to said structure intermediate its expanse, so that said structure provides a moment arm with respect to the hinge axis, and has another member pivotally related to said one member and supported by the supporting means.
 8. Dust collecting apparatus as recited in claim 5, including means resiliently connecting the rigidly interconnected elements with the supporting means.
 9. Dust collecting apparatus as recited in claim 5, wherein there is a plurality of side-by-side series of the dust collecting elements arranged one after the other in file; and means resiliently connecting the said plurality of series with the supporting means in common.
 10. Dust collecting apparatus as recited in claim 6, wherein the series of dust collecting elements are spaced from each other and are rigidly interconnected by one member of the hinge suspension means, another member of said means being pivotally related to said one member and supported by the supporting means.
 11. Dust collecting apparatus as recited in claim 10, wherein the moment arm extends rigidly from adjacent the one member of the hinge suspension.
 12. A method of dislodging accumulated dust from an elongate dust-collecting element, comprising applying vibratory motion to a moment arm attached to the upper end portion of the dust-collecting element, longitudinally of said element and at a location offset laterally therefrom, while freely suspending said element from a hinge axis, said moment arm extending transversely of said hinge axis so as to induce transverse waves that travel downwardly along the length of said element and dislodge said accumulated dust.
 13. A method in accordance with claim 12, wherein the vibratory movement substantially matches a natural frequency of vibration of the dust-collecting element. 